6 months old & aggressive

TLDR: Aggressive puppy toward other dogs and husband and don’t know what to do.

We have a new 6 month old Jack Russel mix. We’ve had him for almost a month. First two weeks were fine. Most recent two weeks he has started being extremely aggressive/reactive towards other dogs both on and off leash. He is also showing aggression to my husband and has tried to bite him twice when my husband tries to handle him. He has also growled at me once. Also – he is not a small Jack Russel. He is 30 pounds so when he is really worked up it is a lot to handle. I am very worried and do not trust him around anyone except for me and my husband. I don’t want to introduce him to anyone or even let maintenance men into my house as I fear he will bite.

We are both regretting getting him ): the shelter said he was super friendly so we were so excited. We would not have adopted a reactive dog since we have nieces and nephews and wanted a family dog.

I’m looking at trainers around my area but am struggling with the right route to take. Lots of trainers use ecollars and swear by them. Then I see other trainers completely disavow the use of them. I feel stuck but I just want to help our pup live his best life. Anyone deal with something similar or have any tips to share?

Thank you!